Build your own ManyChat replacement: auto-DMs on comments with the Meta API

You know the pattern: "Comment LINK and I'll DM you the guide." Behind it is almost always ManyChat — the tool that listens for comments, matches a keyword, and automatically fires off a direct message. Handy, but: a monthly subscription, limits per contact, and your whole funnel — who commented, who got a reply, which links were clicked — runs on someone else's servers.

That mechanic isn't magic. At its core it's a webhook plus one API call. So I built my own "ManyChat replacement" — straight on the official Meta API, with no middleman.

What ManyChat actually does

Boiled down, it's three steps:

1. Listen: someone comments on a post.
2. Match: the comment contains a specific keyword (e.g. "LINK", "GUIDE", "START").
3. Reply: a DM goes out automatically — usually with a link, a lead magnet, or the start of a chat funnel.

The Meta API covers exactly these three steps natively. You don't need ManyChat in between.

How it runs technically

My flow:

• Webhook. Meta sends an event to my server on every new comment (field: comments). For that I subscribe the webhook fields for Instagram (and the Facebook page) inside my Meta app.
• Keyword match. My backend checks the comment text against the stored rules (one rule = keyword + DM text + target link). No match, nothing happens.
• Public reply (Private Reply). The comment gets answered with a Private Reply — that's the trick that opens the DM channel on Instagram. Exactly one Private Reply per comment, and only within 7 days of the comment.
• DM out. The actual message with the link goes to the user through the messaging API.
• Tracking. Every link runs through its own redirect (/go/<code>) that counts clicks — so I see the whole funnel: comment → DM → click.

No messy polling needed: Instagram comments arrive cleanly via webhook. On Facebook I add a light polling fallback, because not every comment event pushes reliably there.

What you need

• A small server with a publicly reachable HTTPS endpoint (for the webhook)
• An Instagram professional account (Business/Creator) linked to a Facebook page
• Your own Meta app in the developer portal — and here's the important part

Important: you need a Meta app — and for real followers, an app review

A dedicated Meta app in the Meta Developer Portal is mandatory: you create it, add the products (Instagram, Facebook Login, Webhooks, Messenger) and subscribe to the comment events. So far it's like the Postiz setup.

But watch out — here's the key difference from a pure scheduling tool: as long as your app is in development mode, sending DMs only works with your own test accounts (app roles: admin/tester). The moment you want to auto-DM real followers, you need Advanced Access for the messaging permissions (instagram_manage_messages, on Facebook pages_messaging) — and that means the app has to go through Meta's app review.

The review wants a screencast showing the full flow (comment → automatic DM), a privacy policy, and a clear use case. Budget a few days for it — Meta reviews manually. It's not a showstopper, but it's the step most people underestimate.

The gotchas

1. The 7-day window. A DM in response to a comment only goes out via the Private Reply, only within 7 days — and exactly once per comment. After that the channel is closed. Ignore it and you get errors that look like "bad token" but actually mean "window closed."
2. Subscribe permissions at account level. Activating the app products isn't enough — you have to set the webhook subscription explicitly per account/page (via graph.instagram.com or the page endpoint), or no events ever arrive.
3. Exact redirect URI. During OAuth the redirect_uri must match the one stored in the app character for character — one missing slash and the login breaks.
4. Rate limits & spam protection. Don't send everyone everything. Meta throttles aggressively, and automated DMs to people who didn't comment a keyword get flagged fast. The keyword condition isn't just convenience — it's your spam protection.

Why it's worth it

• Your funnel is yours. Who commented, who got a reply, which link was clicked how often — all in your own database, not in a subscription's dashboard.
• No price per contact. ManyChat and friends bill by contacts. For you it only costs the server.
• Extensible at will. Because it's your own logic, you can personalize the DM, plug in AI replies, run A/B tests, or write the lead straight into your CRM.

ManyChat is convenient to start with. But the mechanic behind it — webhook, keyword, private reply, DM — is small enough to grasp. Once you've built it yourself, you truly own your funnel: the data, the logic, and every future extension.